JP2015020290A - Thermosensitive recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermosensitive recording material which allows high print density to be obtained, and has excellent sticking resistance.SOLUTION: This invention provides a thermosensitive recording material having, on a support, a thermosensitive recording layer that develops a color by heat, and a protective layer on the thermosensitive recording layer. The protective layer comprises an alkyl ketene dimer with a melting point of 56°C or less, or an olefin-maleic acid resin in an amount of 4 mass% or more relative to the total solid of the protective layer.

Description

  The present invention relates to a heat-sensitive recording material which can obtain a high printing density and has excellent sticking resistance.

  A heat-sensitive recording material generally comprises a support on which a heat-sensitive recording layer mainly composed of an electron-donating usually colorless or light-colored dye precursor and an electron-accepting compound is provided. By heating with light or the like, an electron donating compound as a dye precursor and an electron accepting compound as a developer react instantaneously to obtain a recorded image. Such a heat-sensitive recording material has advantages such as that recording can be obtained with a relatively simple device, easy maintenance, no noise generation, etc., measurement recorder, facsimile, printer, computer terminal, It is used in a wide range of fields such as label printing machines, boarding tickets, and ticket issuing machines. In particular, in recent years, heat-sensitive recording materials are also used for receipts of gas, water, electricity charges, etc., ATM usage statements of financial institutions, various receipts, lotteries, heat-sensitive recording labels or tags for POS systems. It has become.

  As the uses and demands of heat-sensitive recording materials are widely expanded, the use of various barcodes by thermal recording and printing is also increasing, and a heat-sensitive recording material having barcode printing suitability is demanded. In addition, as the amount of information contained in a barcode increases, there is an increasing demand for high-definition barcode printing. However, high-definition barcodes have the problem that the readability is greatly reduced due to slight changes in the width of the bar or space due to printing failure such as sticking, or missing barcode due to white spots in printing. Yes. Further, due to the recent downsizing and power saving of recording devices, there are increasing demands for improving the thermal response and device matching for thermal recording heads. That is, there has been a demand for a heat-sensitive recording material that exhibits the same color density as that of the prior art even at low applied energy due to high speed and low power consumption, and that is free from printing problems such as sticking.

  In order to improve the sticking resistance of the heat-sensitive recording material, it has been proposed to add various fillers to the protective layer. For example, Patent Document 1 discloses a method of adding aluminum hydroxide, Patent Document 2 discloses a method of using kaolin and silicon oxide in combination, and Patent Document 3 discloses kaolin or water. A method of using at least one kind of aluminum oxide in combination with amorphous silica is disclosed. Patent Documents 4 and 5 describe that an alkyl ketene dimer can be used in a heat-sensitive recording layer as a heat-sensitive recording material excellent in water resistance and sticking resistance without providing a protective layer on the heat-sensitive recording layer. Patent Document 6 discloses a method in which a protective layer contains carboxy-modified polyvinyl alcohol, epichlorohydrin resin, modified polyamine / amide resin, and a sizing agent. However, it has been extremely difficult to satisfy both high print density and excellent anti-sticking property.

  On the other hand, Patent Document 7 describes that a backcoat layer having good water resistance can be obtained from a maleic acid resin having a specific molecular weight.

JP-A-6-135149 JP-A-7-9762 Japanese Patent Laid-Open No. 2002-240430 JP 2009-154397 A JP 2009-154448 A JP 2007-223047 A JP 2006-168319 A

  An object of the present invention is to provide a heat-sensitive recording material capable of obtaining a high printing density and having excellent sticking resistance.

(1) In a heat-sensitive recording layer having a heat-sensitive color developing layer on a support and a heat-sensitive recording material having a protective layer on the heat-sensitive recording layer, the protective layer is an alkyl ketene dimer having a melting point of 56 ° C. or lower, or olphine-maleic acid A heat-sensitive recording material comprising a resin in an amount of 4% by mass or more based on the total solid content of the protective layer.

  According to the present invention, it is possible to provide a heat-sensitive recording material which can obtain a high printing density and has excellent sticking resistance.

  The present invention is described in detail below. The present invention provides a heat-sensitive recording material having a protective layer containing 4% by mass or more of an alkyl ketene dimer having a melting point of 56 ° C. or lower or an olphine-maleic acid resin on the total solid content of the protective layer. The present inventors have found that a heat-sensitive recording material having a high printing density and excellent sticking resistance can be obtained.

  In the present invention, the alkyl ketene dimer having a melting point of 56 ° C. or lower is specifically a compound represented by the following formula.

In the formula, R ₁ and R ₂ represent the same or different hydrocarbon groups, and the hydrocarbon group preferably has 8 to 30 carbon atoms, and particularly preferably the hydrocarbon group has 14 to 18 carbon atoms. The melting point of the alkyl ketene dimer is determined by the structure and ratio of the alkyl group, and the melting point of the alkyl ketene dimer made of a linear saturated fatty acid increases as the alkyl chain becomes longer and decreases as the alkyl chain becomes shorter. In addition, the melting point of the alkyl ketene dimer made of a branched chain saturated fatty acid or an unsaturated fatty acid is lower than that of the alkyl ketene dimer made of a straight chain saturated fatty acid having the same carbon number.

  In the present invention, the content of the alkyl ketene dimer having a melting point of 56 ° C. or lower is 4% by mass or more based on the total solid content of the protective layer. More preferably, it is 8.8% by mass or more based on the total solid content of the protective layer. Thereby, a heat-sensitive recording material having particularly excellent sticking resistance can be obtained. The upper limit is preferably 30% by mass or less, particularly preferably 20% by mass or less, based on the total solid content of the protective layer. If this upper limit is exceeded, sufficient print density may not be obtained.

  The olphine-maleic acid resin in the present invention is not particularly limited, and examples thereof include diisobutylene-maleic acid resin, pentene-maleic acid resin, hexene-maleic acid resin, and nonene-maleic acid copolymer. Diisobutylene-maleic acid resin. In the present invention, the content of the orphine-maleic resin is 4% by mass or more based on the total solid content of the protective layer. More preferably, it is 8.8% by mass or more based on the total solid content of the protective layer. Thereby, a heat-sensitive recording material having particularly excellent sticking resistance can be obtained. An upper limit is 30 mass% or less with respect to the total solid of a protective layer, Most preferably, it is 20 mass% or less. If this upper limit is exceeded, sufficient print density may not be obtained.

  In the protective layer according to the present invention, diatomaceous earth, talc, kaolin, calcined kaolin, heavy calcium carbonate, light calcium carbonate, magnesium carbonate, zinc oxide, aluminum oxide, aluminum hydroxide, magnesium hydroxide, titanium dioxide, Inorganic pigments such as barium sulfate, zinc sulfate, amorphous silica, amorphous calcium silicate, colloidal silica, melamine resin, urea-formalin resin, polyethylene, nylon, styrene plastic pigment, acrylic plastic pigment, hydrocarbon Organic pigments such as plastic pigments can be used. Of these, pigments having a plate-like structure such as kaolin and aluminum hydroxide are preferably used. The content of the pigment is preferably 10 to 70% by mass with respect to the total solid components of the protective layer.

  In the protective layer of the present invention, any resin is preferably used as an adhesive. Specific examples include starches, hydroxyethyl cellulose, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, polyacrylic acid ester, polymethacrylic acid ester, polyacrylic acid. Soda, polyethylene terephthalate, polybutylene terephthalate, chlorinated polyether, allyl resin, furan resin, ketone resin, oxybenzoyl polyester, polyacetal, polyetheretherketone, polyethersulfone, polyimide, polyamide, polyamideimide, polyaminobismaleimide, poly Methylpentene, polyphenylene oxide, polyphenylene sulfide, polyphenylene sulfone, police Hong, polyarylate, polyallylsulfone, polybutadiene, polycarbonate, polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyurethane, phenol resin, urea resin, melamine resin, melamine formalin resin, benzoguanamine resin, bis Maleimide triazine resin, alkyd resin, amino resin, epoxy resin, unsaturated polyester resin, styrene / butadiene copolymer, acrylonitrile / butadiene copolymer, methyl acrylate / butadiene copolymer, ethylene / vinyl acetate copolymer, acrylic Acid amide / acrylic acid ester copolymer, acrylic acid amide / acrylic acid ester / methacrylic acid terpolymer, alkali salt of styrene / maleic anhydride copolymer, Various polyolefin resins, and the like. These may be used alone or as a mixture of two or more. In this invention, 50-95 mass% is preferable with respect to the total solid of a protective layer, and, as for content of the adhesive agent in a protective layer, 60-90 mass% is especially preferable.

  The heat-sensitive recording layer according to the present invention is obtained by mixing each aqueous dispersion obtained by finely pulverizing each color developing component and a resin, and coating and drying on a support.

  The electron-donating compounds that are usually colorless to light-colored dye precursors contained in the heat-sensitive recording layer are typically represented by pressure-sensitive recording materials and those used in heat-sensitive recording materials, but are particularly limited. is not.

As an example of a specific dye precursor,
(1) Triarylmethane compounds: 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (crystal violet lactone), 3,3-bis (p-dimethylaminophenyl) phthalide, 3- (P-dimethylaminophenyl) -3- (1,2-dimethylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3- (P-dimethylaminophenyl) -3- (2-phenylindol-3-yl) phthalide, 3,3-bis (1,2-dimethylindol-3-yl) -5-dimethylaminophthalide, 3,3 -Bis (1,2-dimethylindol-3-yl) -6-dimethylaminophthalide, 3,3-bis (9-ethylcarbazol-3-yl)- -Dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -5-dimethylaminophthalide, 3-p-dimethylaminophenyl-3- (1-methylpyrrol-2-yl)- 6-dimethylaminophthalide, etc.

  (2) Diphenylmethane compounds: 4,4′-bis (dimethylaminophenyl) benzhydrylbenzyl ether, N-chlorophenylleucooramine, N-2,4,5-trichlorophenylleucooramine, etc.

  (3) Xanthene compounds: Rhodamine B anilinolactam, rhodamine Bp-chloroanilinolactam, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-octylaminofluorane, 3-diethylamino- 7-phenylfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-chloro-7-methylfluorane, 3-diethylamino-6-methyl-7- (3-methylphenylamino) fluorane, 3 -Diethylamino-7- (3,4-dichloroanilino) fluorane, 3-dibutylamino-7- (2-chloroanilino) fluorane, 3-diethylamino-7- (2-chloroanilino) fluorane, 3-diethylamino-6-methyl -7-anilinofluorane, 3-dibutyla No-6-methyl-7-anilinofluorane, 3-dipentylamino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N-tolyl) amino-6-methyl-7-anilino Fluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N-tolyl) amino-6-methyl-7-phenethylfluorane, 3-diethylamino-7- (4- Nitroanilino) fluorane, 3- (N-methyl-N-propyl) amino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluor Oran, 3- (N-methyl-N-cyclohexyl) amino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N-tetrahydrofurfuryl) amino-6-methyl-7- Nirinofuruoran, 3-diethylamino-6-methyl-7- (3-trifluoromethyl) -6-fluoran and the like,

  (4) Thiazine compounds: benzoyl leucomethylene blue, p-nitrobenzoyl leucomethylene blue, etc.

  (5) Spiro compounds: 3-methylspirodinaphthopyrans, 3-ethylspirodinaphthopyrans, 3,3'-dichlorospirodinaphthopyrans, 3-benzylspirodinaphthopyrans, 3-methylnaphtholopyrans (3-methoxy) Benzo) spiropyran, 3-propyl spirobenzopyran and the like. These dye precursors can be used alone or in admixture of two or more as required.

  As the electron-accepting compound that is a developer contained in the heat-sensitive recording layer, a pressure-sensitive recording material or an acidic substance generally used in a heat-sensitive recording material can be used, but is not particularly limited. For example, phenol derivatives, aromatic carboxylic acid derivatives, N, N′-diarylthiourea derivatives, arylsulfonylurea derivatives, polyvalent metal salts such as zinc salts of organic compounds, benzenesulfonamide derivatives, urea urethane compounds, etc. Can do.

  Specific examples of the electron-accepting compound contained in the heat-sensitive recording layer are listed below, but are not necessarily limited to these compounds.

  4-hydroxy-4'-isopropoxydiphenylsulfone, 4-hydroxy-4'-n-propoxydiphenylsulfone, 4,4'-dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, 4-hydroxydiphenylsulfone, 4 -Hydroxy-4'-methyldiphenylsulfone, 4-hydroxy-4'-methoxydiphenylsulfone, 4-hydroxy-4'-ethoxydiphenylsulfone, 4-hydroxy-4'-n-butoxydiphenylsulfone, 4-hydroxy-4 '-Benzyloxydiphenylsulfone, bis (4-hydroxyphenyl) sulfone monoallyl ether, bis (3-allyl-4-hydroxyphenyl) sulfone, bis (3,5-dibromo-4-hydroxyphenyl) sulfone, bis (3 , -Dichloro-4-hydroxyphenyl) sulfone, 3,4-dihydroxydiphenylsulfone, 3,4-dihydroxy-4'-methyldiphenylsulfone, 3,4,4'-trihydroxydiphenylsulfone, 4,4 '-[oxybis (Ethyleneoxy-p-phenylenesulfonyl)] diphenol, 3,4,3 ′, 4′-tetrahydroxydiphenylsulfone, 2,3,4-trihydroxydiphenylsulfone, 3-phenylsulfonyl-4-hydroxydiphenylsulfone, 2,4-bis (phenylsulfonyl) phenol,

  4-phenylphenol, 4-hydroxyacetophenone, 1,1-bis (4-hydroxyphenyl) propane, 1,1-bis (4-hydroxyphenyl) pentane, 1,1-bis (4-hydroxyphenyl) hexane, , 1-bis (4-hydroxyphenyl) cyclohexane, 2,2-bis (4-hydroxyphenyl) propane, 2,2-bis (4-hydroxyphenyl) hexane, 1,1-bis (4-hydroxyphenyl)- 2-ethylhexane, 2,2-bis (3-chloro-4-hydroxyphenyl) propane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 1,3-bis [1- (4- Hydroxyphenyl) -1-methylethyl] benzene, 1,3-bis [1- (3,4-dihydroxyphenyl) -1-methyl ester L] benzene, 1,4-bis [1- (4-hydroxyphenyl) -1-methylethyl] benzene, 4,4'-dihydroxydiphenyl ether, 3,3'-dichloro-4,4'-dihydroxydiphenyl sulfide, Bis (2-hydroxynaphthyl) methane,

  2,2-bis (4-hydroxyphenyl) methyl acetate, 2,2-bis (4-hydroxyphenyl) butyl acetate, 4,4-thiobis (2-tert-butyl-5-methylphenol), 4-hydroxyphthal Dimethyl acid, benzyl 4-hydroxybenzoate, methyl 4-hydroxybenzoate, benzyl gallate, stearyl gallate, pentaerythritol tetra (4-hydroxybenzoic acid) ester, pentaerythritol tri (4-hydroxybenzoic acid) ester, N Dehydration condensate of 4-butyl-4- [3- (p-toluenesulfonyl) ureido] benzoate, 2,2-bis (hydroxymethyl) -1,3-propanediol polycondensate and 4-hydroxybenzoic acid,

  N, N'-diphenylthiourea, 4,4'-bis [3- (4-methylphenylsulfonyl) ureido] diphenylmethane, N- (4-methylphenylsulfonyl) -N'-phenylurea, N- (benzenesulfonyl) ) -N '-[3- (4-toluenesulfonyloxy) phenyl] urea, N- (4-toluenesulfonyl) -N'-[3- (4-toluenesulfonyloxy) phenyl] urea, urea urethane compound,

  Salicylanilide, 5-chlorosalicylanilide, salicylic acid, 3,5-di-tert-butylsalicylic acid, 3,5-bis (α-methylbenzyl) salicylic acid, 4- [2 ′-(4-methoxyphenoxy) ethyloxy] salicylic acid , 3- (octyloxycarbonylamino) salicylic acid or metal salts (for example, zinc salts) of these salicylic acid derivatives,

  N- (4-hydroxyphenyl) -4-toluenesulfonamide, N- (2-hydroxyphenyl) -4-toluenesulfonamide, N-phenyl-4-hydroxybenzenesulfonamide and the like.

  The heat-sensitive recording layer can contain a heat-fusible substance as a sensitizer in order to improve its thermal response. In this case, those having a melting point of 60 to 180 ° C are preferable, and those having a melting point of 80 to 140 ° C are more preferably used.

  Specifically, stearic acid amide, palmitic acid amide, behenic acid amide, N-hydroxymethyl stearic acid amide, N-stearyl stearic acid amide, ethylene bis stearic acid amide, methylene bis stearic acid amide, methylol stearic acid amide, N -Stearyl urea, benzyl-2-naphthyl ether, m-terphenyl, 4-benzylbiphenyl, 2,2'-bis (4-methoxyphenoxy) diethyl ether, α, α'-diphenoxy-o-xylene, bis (4 -Methoxyphenyl) ether, diphenyl adipate, dibenzyl oxalate, bis (4-methylbenzyl) oxalate, bis (4-chlorobenzyl) oxalate, dimethyl terephthalate, dibenzyl terephthalate, phenylbenzenesulfonate Known heat such as stealth, bis (4-allyloxyphenyl) sulfone, 1,2-bis (3-methylphenoxy) ethane, 1,2-diphenoxyethane, 4-acetylacetophenone, acetoacetate anilides, fatty acid anilides, etc. Examples of fusible substances include higher fatty acid amides, which are more preferable because they function as lubricants.

  These compounds can be used alone or in combination of two or more. In order to obtain sufficient thermal responsiveness, it is preferable that the sensitizer occupies 5 to 50% by mass in the total solid content of the thermosensitive recording layer.

  In the heat-sensitive recording material of the present invention, one or more intermediate layers can be provided between the support and the heat-sensitive recording layer as necessary, for example, to increase the color development sensitivity. In addition, one or more back coat layers such as a magnetic recording layer, an antistatic layer, and an adhesive layer can be provided on the opposite surface (back surface) of the thermosensitive recording layer with the support interposed therebetween.

  Other than the protective layer described above, for example, diatomaceous earth, talc, kaolin, calcined kaolin, heavy calcium carbonate, light calcium carbonate, magnesium carbonate, zinc oxide as a pigment for the support and optional layers (intermediate layer and back coat layer) Inorganic pigments such as aluminum oxide, aluminum hydroxide, magnesium hydroxide, titanium dioxide, barium sulfate, zinc sulfate, amorphous silica, amorphous calcium silicate, colloidal silica, melamine resin, urea-formalin resin, polyethylene, Organic pigments such as nylon, styrene plastic pigments, acrylic plastic pigments, and hydrocarbon plastic pigments can be used together with an adhesive. In particular, the calcined kaolin and / or organic hollow pigment is preferable as the intermediate layer pigment, and a heat-sensitive recording material having excellent heat response due to high heat insulation can be obtained. When an organic hollow pigment is used, by including air in the hollow part, higher heat insulation is obtained, and since the pigment shape is close to a sphere, it can be arranged densely without impairing the flexibility of the layer, Since an intermediate layer having both high strength and flexibility can be obtained, excellent thermal response and surface strength are exhibited. The organic hollow pigment in the present invention refers to a resin pigment having a closed space inside the pigment, vinyl chloride, vinylidene chloride, vinyl acetate, styrene, methyl acrylate, ethyl acrylate, butyl acrylate, acrylonitrile, methyl methacrylate. , Homopolymers mainly composed of monomers such as ethyl methacrylate, butyl methacrylate and methacrylonitrile, and copolymers composed of two or more of the aforementioned monomers. The organic hollow pigment used in the present invention is not particularly limited within the scope of the effect of the present invention, but preferably has an average particle diameter of 0.1 to 5.0 μm by a particle size distribution measuring method of a laser diffraction method. Furthermore, the thing of 0.5-2.0 micrometers is more preferable. Moreover, 3-80 mass% of content of these organic hollow pigments is preferable with respect to the total solid of an intermediate | middle layer.

  Moreover, arbitrary resin is used for a support body and arbitrary layers (an intermediate | middle layer and a backcoat layer) as an adhesive agent. Specific examples include starches, hydroxyethyl cellulose, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, polyacrylic acid ester, polymethacrylic acid ester, polyacrylic acid. Soda, polyethylene terephthalate, polybutylene terephthalate, chlorinated polyether, allyl resin, furan resin, ketone resin, oxybenzoyl polyester, polyacetal, polyetheretherketone, polyethersulfone, polyimide, polyamide, polyamideimide, polyaminobismaleimide, poly Methylpentene, polyphenylene oxide, polyphenylene sulfide, polyphenylene sulfone, police Hong, polyarylate, polyallylsulfone, polybutadiene, polycarbonate, polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyurethane, phenol resin, urea resin, melamine resin, melamine formalin resin, benzoguanamine resin, bis Maleimide triazine resin, alkyd resin, amino resin, epoxy resin, unsaturated polyester resin, styrene / butadiene copolymer, acrylonitrile / butadiene copolymer, methyl acrylate / butadiene copolymer, ethylene / vinyl acetate copolymer, acrylic Acid amide / acrylic acid ester copolymer, acrylic acid amide / acrylic acid ester / methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, ethylene Alkali salts or ammonium salts of on / maleic anhydride copolymer, other various polyolefin resins.

  The protective layer and / or the heat-sensitive recording layer preferably contains a lubricant such as a higher fatty acid metal salt, a higher fatty acid amide, paraffin, polyolefin, polyethylene oxide, or caster wax for the purpose of improving sticking properties. The content of the lubricant is preferably 5 to 50% by mass with respect to the total solid content of the protective layer or the heat-sensitive recording layer. In addition, for the purpose of improving light resistance, the protective layer and / or the thermosensitive recording layer is an interface containing an anionic or nonionic high molecular weight as a UV absorber such as benzophenone or benzotriazole, or a dispersing / wetting agent. An activator, further a fluorescent dye, an antifoaming agent, and the like are added as necessary.

  As the support according to the present invention, paper, various woven fabrics, non-woven fabrics, synthetic resin films, synthetic resin laminated papers, synthetic papers, metal foils, vapor-deposited sheets, or composite sheets in which these are bonded together are used depending on the purpose. Can be used arbitrarily. Among these, paper such as neutral paper and acid paper is particularly preferably used because the water content can be easily controlled.

The method for forming the heat-sensitive recording layer, the protective layer, the intermediate layer, or the backcoat layer provided as necessary is not particularly limited, and can be formed according to a conventionally known technique. As specific examples, coating liquid is applied by methods such as film press coating, air knife coating, rod blade coating, bar coating, blade coating, gravure coating, curtain coating, E-bar coating, etc. Each layer can be formed by drying. In addition, each layer may be formed by various printing machines or the like using a system such as a lithographic plate, a relief plate, a flexo, a gravure, a screen, and a hot melt. Furthermore, each layer may be applied and dried sequentially, or each layer may be applied and dried (wet-on-wet), and each layer may be applied and dried simultaneously. (Multilayer simultaneous coating by slide curtain coating). The coating amount of the thermosensitive recording layer is usually preferably 0.05 to 2.0 g / m ^{2 in} terms of the absolutely dry coating amount of the dye precursor in order to obtain sufficient thermal response. 0 g / m ² is more preferable. Ze'inuinurikoryou protective layer is preferably ^{0.2~10g / m 2, 1~5g / m} 2 is more preferable. Ze'inuinurikoryou intermediate layer is preferably ^{1~30g / m 2, 3~20g / m} 2 is more preferable. The absolute dry coating amount of the backcoat layer is appropriately selected depending on the required function and the like.

  If necessary, the printing image quality can be improved by supercalendering after intermediate layer coating, after heat-sensitive recording layer coating, after protective layer coating, or after backcoat layer coating.

  Next, the present invention will be described in more detail with reference to examples. However, it is not limited to these. The parts and% shown below are based on mass, and the coating amount is the absolute dry coating amount.

Example 1
(1) Preparation of coating liquid for intermediate layer Firing kaolin [manufactured by BASF: trade name Ancilex] 50 parts, organic hollow pigment particle dispersion liquid having a solid content concentration of 27.5% [manufactured by Rohm and Haas: trade name HP91] A composition comprising 100 parts, 40 parts of 50% styrene / butadiene latex, 50 parts of a 10% aqueous oxidized starch solution and 100 parts of water was mixed and stirred to prepare an intermediate layer coating solution.

(2) Preparation 1 of thermal recording layer coating liquid
Each of the following (A), (B) and (C) mixed liquids was pulverized with a dynomill (a sand mill manufactured by WAB Co., Ltd.) so as to have an average particle diameter of 1 μm or less to obtain each dispersion.
(A) Dye precursor dispersion 3-dibutylamino-6-methyl-7-anilinofluorane 30 parts 2.5% sulfone-modified polyvinyl alcohol aqueous solution 69 parts 1% acetylene glycol surfactant aqueous solution 1 part (B) Electron-accepting compound dispersion 4-hydroxy-4'-isopropoxydiphenylsulfone 30 parts 2.5% sulfone-modified polyvinyl alcohol aqueous solution 69 parts 1% acetylene glycol surfactant aqueous solution 1 part (C) Pigment / sensitizer dispersion Liquid Aluminum hydroxide (made by Showa Denko Co., Ltd .: trade name Hydylite H42) 50 parts 1,2-bis (3-methylphenoxy) ethane 30 parts 2.5% sulfone-modified polyvinyl alcohol aqueous solution 199 parts 1% acetylene glycol-based surface activity 1 part aqueous solution

(3) Preparation of heat-sensitive recording layer coating liquid 2
Next, in addition to the dispersions (A), (B), and (C), the following were mixed and stirred to prepare a thermal recording layer coating solution.
(A) Dye precursor dispersion 100 parts (B) Electron accepting compound dispersion 100 parts (C) Pigment / sensitizer dispersion 280 parts 30% zinc stearate aqueous dispersion [manufactured by Chukyo Yushi Co., Ltd .: trade name Z -7-30] 25 parts 40% methylol stearamide aqueous dispersion 25 parts 20% paraffin wax aqueous dispersion 25 parts 10% fully saponified polyvinyl alcohol [manufactured by Kuraray Co., Ltd .: trade name PVA117] aqueous solution 200 parts water 100 parts

(4) Preparation of protective layer coating liquid A protective layer coating liquid was prepared by mixing in the following composition.
10% polyvinyl alcohol [manufactured by Kuraray Co., Ltd .: trade name PVA117, average polymerization degree: about 1700] aqueous solution 100 parts 20% kaolin [manufactured by BASF: UW90] aqueous dispersion 15 parts 30% zinc stearate aqueous dispersion [Chukyo Yushi Co., Ltd. Product name: Z-7-30] 4 parts 20% alkyl ketene dimer [manufactured by Seiko PMC Co., Ltd .: product name SS 362 (mixture of alkyl ketene dimers having a linear alkyl chain of C16 to C18) melting point: 50 ° C.] 4 parts 60 parts water

(5) Production of heat-sensitive recording material A neutral high-quality paper roll having a basis weight of 66 g / m ² has a solid coating amount of 5 g / m ² for the intermediate layer coating solution and a solid coating of the heat-sensitive recording layer coating solution. Air knife coater and air floating dryer so that the coating amount is 0.5 g / m ^{2 in} terms of the coating amount of the dye precursor, and the solid content coating amount of the coating liquid for the protective layer is 2 g / m ^2. Was coated and dried, and calendered to produce a thermosensitive recording material. The temperature of the surface of the heat-sensitive recording layer after coating the coating solution for heat-sensitive recording layer and drying was 60 ° C., and the protective layer was coated on the heat-sensitive recording layer having such a surface temperature.

Example 2
Thermosensitive recording was performed in the same manner as in Example 1 except that 4 parts of 20% alkyl ketene dimer (manufactured by Starlight PMC: trade name SS362) was changed to 10 parts in the preparation of the coating liquid for protective layer (4) of Example 1. The material was made.

Example 3
20% alkyl ketene dimer [Arakawa Chemical Industries, Ltd.] instead of 4 parts of 20% alkyl ketene dimer [manufactured by Seiko PMC Co., Ltd .: trade name SS362 melting point: 50 ° C.] Product name: Size Pine K-903 (mixture of alkyl ketene dimer having a linear alkyl chain of C16 to C18) Melting point: 38 ° C.] Heat sensitive in the same manner as in Example 1 except that 10 parts were used. A recording material was prepared.

Example 4
In the preparation of the coating solution for protective layer (4) in Example 1, instead of 4 parts of 20% alkyl ketene dimer (trade name SS362), 25% alkyl ketene dimer (trade name: Seiko PMC) SE2395 (mixture of alkyl ketene dimers having a branched alkyl chain having 14 to 16 carbon atoms) Melting point: 10 ° C. or lower] A thermosensitive recording material was produced in the same manner as in Example 1 except that 8 parts were used.

Example 5
In the preparation of the coating solution for protective layer (4) of Example 1, 20% alkyl ketene dimer [manufactured by Seiko PMC: trade name SS362] instead of 4 parts, 25% olphine-maleic acid resin (manufactured by Arakawa Chemical Industries, Ltd.) : Brand name Polymalon 482S (diisobutylene-maleic acid resin)] A thermosensitive recording material was produced in the same manner as in Example 1 except that 3.2 parts were used.

Example 6
In the preparation of the coating solution for protective layer (4) of Example 1, 20% alkyl ketene dimer [manufactured by Seiko PMC: trade name SS362] instead of 4 parts, 25% olphine-maleic acid resin (manufactured by Arakawa Chemical Industries, Ltd. : Brand name Polymalon 482S (diisobutylene-maleic acid resin)] A heat-sensitive recording material was prepared in the same manner as in Example 1 except that 8 parts were used.

Example 7
In the preparation of the coating solution for protective layer (4) of Example 1, 20% alkyl ketene dimer [manufactured by Seiko PMC: trade name SS362] instead of 4 parts, 21.8% olphine-maleic acid resin [Rohm and Haas] Company name: Orotan 165A (diisobutylene-maleic acid resin)] 9.2 parts was used in the same manner as in Example 1 except that 9.2 parts were used.

Comparative Example 1
A thermosensitive recording material was prepared in the same manner as in Example 1 except that 20% alkyl ketene dimer [manufactured by Seiko PMC: trade name SS362] was not added in the preparation of the coating liquid for protective layer (4) of Example 1. Produced.

Comparative Example 2
In the preparation of the coating solution for protective layer (4) of Example 1, 20% alkyl ketene dimer [manufactured by Seiko PMC Co., Ltd .: trade name SS362], except that 4 parts was changed to 2 parts except for feeling Produced a thermosensitive recording material in the same manner as in Example 1.

Comparative Example 3
In the preparation of the coating liquid for protective layer (4) in Example 1, instead of 4 parts of 20% alkyl ketene dimer [manufactured by Starlight PMC: trade name SS362], 25% styrene-acrylic resin [manufactured by Harima Kasei Co., Ltd .: commodity Nominal size LX-530] A thermosensitive recording material was produced in the same manner as in Example 1 except that 3.2 parts were used.

Comparative Example 4
In the preparation of the coating solution for protective layer (4) in Example 1, 20% alkyl ketene dimer [manufactured by Seiko PMC Co., Ltd .: trade name SS362 melting point: 50 ° C.] instead of 4 parts, 30% alkyl ketene dimer [Seiko PMC Co., Ltd.] Product name: AD1604 (mixture of alkyl ketene dimers having a straight chain alkyl chain of C16 to C18) Melting point: 62 ° C.] A thermosensitive recording material was prepared in the same manner as in Example 1 except that 2.67 parts were used. Produced.

Comparative Example 5
In the preparation of the coating solution for protective layer (4) of Example 1, 20% alkyl ketene dimer [manufactured by Seiko PMC: trade name SS362] instead of 4 parts, 25% olphine-maleic acid resin (manufactured by Arakawa Chemical Industries, Ltd.) : Brand name Polymaron 482S] A heat-sensitive recording material was produced in the same manner as in Example 1 except that 1.6 parts were used.

  The following evaluation was performed about the thermosensitive recording material produced in the above Examples 1-7 and Comparative Examples 1-5. The results are shown in Table 1.

[Print density]
Each of the produced thermal recording materials was printed using a facsimile testing machine TH-PMD manufactured by Okura Electric Co., Ltd. Using a thermal head having a dot density of 8 dots / mm and a head resistance of 1685Ω, solid black and characters were printed with an applied voltage of 20 volts and an applied pulse width of 1.6 msec. The print density was measured with a Macbeth RD-918 reflection densitometer (visual filter) (manufactured by Macbeth). The numerical value of the print density is practically 1.0 or more, preferably 1.2 or more.

[Sticking resistance]
Using a printer manufactured by Canon Inc., trade name Prea CT-1, a solid black pattern was printed under an environmental condition of 5 ° C., and a horizontal printing failure due to sticking was evaluated. The evaluation criteria followed the following indicators.
◎: Sticking does not occur at all ○: Printing failure due to sticking hardly occurs △: Printing failure due to sticking occurs and there is a problem in actual use ×: Printing failure due to sticking occurs over the entire surface

  As is apparent from Table 1, it can be seen that a heat-sensitive recording material having a high print density and excellent sticking resistance can be obtained by the present invention.

Claims (1)

  In a thermosensitive recording material having a heat-sensitive recording layer that develops color by heat on a support and a protective layer on the thermosensitive recording layer, the protective layer protects an alkyl ketene dimer or olphine-maleic acid resin having a melting point of 56 ° C. or lower. A heat-sensitive recording material comprising 4% by mass or more based on the total solid content of the layer.